I've checked many websites to be inspired about what the look and feel of a serious enterprise web-application should look like. But the whole I saw were designed for being used by single users and not serious corporate users. The designs I saw were mostly happy-colored, and looked like being developed by a small team of eager young passionate developers.

But what I'm looking for, are showcases of serious web apps' designs (e.g. web apps developed by large corporations) that are developed for being used by a large number of corporate uses.

Can you suggest me sources for this kind of inspiration?